It has long been known in the art to form ionically conducting polymer electrolyte membranes and gels from organic polymers containing ionic pendant groups. Well-known so-called ionomer membranes in widespread commercial use are Nafion® perfluoroionomer membranes available from E.I. du Pont de Nemours and Company, Wilmington Del. Nafion® is formed by copolymerizing tetrafluoroethylene (TFE) with perfluoro(3,6-dioxa-4-methyl-7-octenesulfonyl fluoride), as disclosed in U.S. Pat. No. 3,282,875. Other well-known perfluoroionomer membranes are copolymers of TFE with perfluoro(3-oxa-4-pentene sulfonyl fluoride), as disclosed in U.S. Pat. No. 4,358,545. The copolymers so formed are converted to the ionomeric form by hydrolysis, typically by exposure to an appropriate aqueous base, as disclosed in U.S. Pat. No. 3,282,875. Lithium, sodium and potassium are all well known in the art as suitable cations for the above cited ionomers.
Low equivalent weight is necessary to obtain high conductivity, but this could cause poor mechanical properties. One approach to solve these problem is to make new cyclic polymers which usually have high glass transition temperature (“Tg”) and good mechanical properties.
Free radical polymerizations which include nonconjugated dienes (and bis vinyl ethers) usually yield polymers which are crosslinked because of the “separate” reaction of each of the double bonds with the free radicals in the reactions. However, it is known that in some instances perfluorinated or partially fluorinated compounds containing two such double bonds do not form crosslinked polymers, but form polymers containing cyclic structures.
In U.S. Pat. Nos. 6,214,955 and 6,255,543 selected partially fluorinated monomers and the corresponding polymers were prepared. However, these polymers were not made into films and also did not contain any ionomeric substituents.
What is needed, therefore, are new cyclic, fluorinated monomers and polymers that can be formed into conductive films with good mechanical properties.